The invention relates to a pipe-connection molded part for pre-insulated pipe conduits of plastic material, the pipe conduit being pre-insulated with polyurethane foam.
In pipe conduit construction, in particular in applications in which good insulation of the medium relative to the environment is required, such as, for example, in pipe conduit systems for the transport of refrigerants, pre-insulated pipe conduit sections are being increasingly used. A readily suitable material for the insulation of refrigerant pipe conduits is foamed polyurethane. Arranged around the pipe conduit is an outer pipe or a tubular outer casing which is kept at a uniform distance from the outer wall of the pipe conduit concentrically around the pipe conduit by means of spacers. The annular space between the inner wall of the casing and the outer wall of the pipe conduit is completely filled with polyurethane foam. The polyurethane foam is injected as a reactive foam-forming liquid, and the foam produced hardens. The foam readily adheres to the surfaces of the pipe conduit and the outer casing and also gives the pipe conduit pre-insulated in this way greater rigidity.
If a plurality of such pipe conduit sections have to be connected to one another, the effort required for preparing and producing the pipe conduit connection is relatively large. The pipe conduit itself must be exposed, cleaned of foam and connected to the next pipe conduit section by means of a sleeve. The outer casing must be made continuous again by means of a heat-shrinkable tube around the connection point, and the annular intermediate space between outer casing and the point connected to the sleeve must be filled with new foam.
EP182604 B1 discloses an arrangement and a method for connecting pipe conduits pre-insulated with polyurethane foam. In the insulating material in the intermediate space between pipe conduit and outer casing, an annular space is formed at the connection point. A special annular element which shrinks under the action of heat is introduced in this annular space. The special element consists of a nickel-titanium alloy. After the shrink-fit operation, the annular element exerts such a high force on the connection point between the two pipe conduits that no further connection of the pipe conduits is necessary.
Instead of the special element, a commercially available sleeve or adhesive sleeve may also be used. To this end, the polyurethane foam must also be removed from the connection region before the connection is produced. In order to obtain a sound connection between sleeve and pipe, the outside of the inner pipe must be peeled with a special peeling implement and cleaned.
Based on the prior art, the object of the invention is to provide a pipe-connection molded part for pre-insulated pipe conduits which permits a medium-tight, cost-effective and environmentally safe connection between two pipe conduit sections at any desired point of the pipe conduit.